Shifting Baselines (or the problem of sliding targets in conservation)

Transcription

1 Shifting Baselines (or the problem of sliding targets in conservation) C. Roberts

2 Change is Happening Retreating Glaciers Parks Canada "New Mexico Lake (1991 and 2001)" S. Glover

3 Shifting Baselines Shifting baselines are the chronic, slow, hard-to-notice changes in things, from the disappearance of birds and frogs in the countryside to the increased drive time from L.A. to San Diego. If your ideal weight used to be 150 pounds and now it is 160, your baseline -- as well as your waistline -- has shifted. The term was coined by fisheries biologist Daniel Pauly in 1995, and it quickly spread to a variety of disciplines. It has been applied to analysis of everything from deteriorating cities to declining quality of entertainment. (text from Randy Olson, LA Times Opinion Piece, 2002) (

4 "Florida Corals" E.A. Shinn, USGS "Corals ( )" Craig Quirolo

5 Implications of Shifting Baselines Emerging Consensus: The baselines have shifted for many ocean ecosystems. Without knowledge of the past, each new generation accepts the current baselines (that have already shifted) as the norm. Three Unresolved Issues: 1. Detection: Is Change Happening? How fast? 2. Prediction: What will nature look like in the future? 3. Management: What should (restored) nature look like?

6 Pristine What does it mean? The word "pristine" is used widely in advertising (take a look at ads for bottled water) to describe "untouched" portions of nature. How should the pristine ocean look like? When did this original reference state occur? Fifteen thousand years ago? Certainly different from today -- the North Atlantic was frozen solid. Two hundred million years ago? There were enormous reefs made of giant clams. Six hundred and fifty million years ago? Nothing but jellyfish and bacteria. A billion years ago? Nothing but bacteria.

7 How About 100 Years Ago? Different from today? Yes For instance the whalers of Nantucket had driven gray whales in the North Atlantic to extinction, and were whaling in the South Pacific. Steller's sea cow extinct for over 100 years and Great Auks for 50. Steller's sea cow (Hydrodamalis gigas) Great Auk, (Pinguinus impennis) Last certain record on July 1844 on Iceland, First described in Hunted to extinction within 27 years of discovery by Europeans.

8 How About 500 Years Ago? Were humans exploiting the ocean 500 years ago? Yes: Basque cod fishers were travelling to Newfoundland, and had already extirpated the Northeast Atlantic Right Whale. How about the native americans? This is a scene created using several historical accounts from explorers: By day, the natives used a dip net and spear, and by night, a fire in a canoe to attract the fish to the boat. They also employed fish weirs to trap fish. From the British Museum: John White The manner of their fishing, North America, ~AD

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10 Benchmarks, Baselines,Trends, Regime Shifts The detection of trends in ecosystems depends upon: (1) good description of benchmarks for measuring variability Sensitive, cost-effective, easy to interpret (2) ability to distinguish between natural / anthropogenic changes Natural areas (for controls) How far back should we go? How long is the right baseline? What are the natural patterns of variability? How large of a human impact do we want to detect?

11 Shifting Baselines & Reduced Expectations The Shifting Baseline Syndrome (Pauly 1995) Essentially, this syndrome has arisen because each generation of fisheries scientists accepts as a baseline the stock size and species composition that occurred at the beginning of their careers, and uses this to evaluate changes. When the next generation starts its career, the stocks have further declined, but it is the stocks at that time that serve as a new baseline. The result obviously is a gradual shift of the baseline, a gradual accommodation of the creeping disappearance of resource species, and inappropriate reference points for evaluating economic losses resulting from overfishing, or for identifying targets for rehabilitation measures.

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13 Sliding Baselines and Anecdotes Importance of the Historical Dimension in Policy and Management (Pauly 2001)

14 How to Deal With Shifting Baselines Anecdotes and the shifting baseline syndrome of fisheries (Pauly 1995) Developing frameworks for incorporation of earlier knowledge into present models of fisheries Adding historical knowledge to a discipline that has suffered from lack of historical perspective Frameworks that maximize the use of fisheries history will help understand and overcome the shifting baselines syndrome

15 Sliding Baselines and Anecdotes Reefs before Columbus (Jackson 1997) How many turtles lived in the Caribbean in 1492?

16 Sliding Baselines and Anecdotes Reefs before Columbus (Jackson 1997) Modelling Approaches: - Historical catches (6.5 million) - Carrying capacity models (660 million) New Approaches: - Middens / isotopic analyses - Genetics (Ne): museum samples

17 Generational / Personal Amnesia Evidence for SBS in Conservation Biology (Papworth et al. 2009) Two Explanations for SBS: - Generational Amnesia: New generations blind to change - Personal Amnesia: Old generation fails to remember

18 Generational / Personal Amnesia Evidence for SBS in Conservation Biology (Papworth et al. 2009) Attempts to collect qualitative and quantitative data - Time of Change - Trends (Relative Abundance)

19 Sliding Baselines & Reduced Expectations Ghost Forests (Dayton et al. 1998) ing_resources/kelp_forest,_ghost_forest/ Fifty years ago, the Southern California kelp forests, were home to a remarkable number of large fish and invertebrates. 400-pound black sea bass, 100-pound groupers, 20- pound lobsters lived through the kelp s towering fronds. The absence of once common marine organisms, especially the scarcity of the largest ones, has prompted the term ghost forests

20 California Kelp Beds Dominant predators in the system have been removed 1950s 2000s Commercial and sport (logbook) landings of white sea bass (Atractoscion noblis) in Southern CA

21 Sliding Baselines & Reduced Expectations Kelp forest urchin predators over-harvested (Dayton et al. 1998)

22 Point Loma Kelp Bed History Project Program started in 1971 (Dayton et al., 1984). Natural disturbances, notably storms, El Niños, and grazing, caused major fluctuations in distribution and abundance of kelps, especially giant kelp, Macrocystis pyrifera. Plants affected by gradients in depth, light, temperature, water motion, nutrient availability, and planktonic propagule supply.

23 Point Loma Kelp Bed History Project Storm mortality is strongly depth / location dependent (Dayton et al. 1992). Significant longshore variability as well: kelp plants on the ends of the forest suffer much higher storm-related mortality than plants in center of the forest. Conversely, the edges of the forest have better kelp survivorship than the central site (at the same depth) during El Niño summers; (Tegner & Dayton 1987).

24 Ocean Climate Effects on Kelp Beds Definition of a meaningful benchmark is impossible, because many of the large animals have been gone for years to decades, and kelps are sensitive to large-scale, low-frequency El Nin o Southern Oscillation events and longer term regime shifts

25 Ocean Climate Effects on Kelp Beds A shift in the oceanographic climate has significantly reduced the average size and carrying capacity of the dominant plant

26 Macrocystis stipe data showing important changes between the ocean climate in late 1950s / early 1970s and 1980s / 1990s Results consistent with larger scale California Current picture Suggest a regime shift in mid-tolate 1970s Ocean Climate Effects on Kelp Beds

27 California Kelp Forests - Conclusions A shift in the oceanographic climate has significantly reduced the average size and carrying capacity of the dominant plant. Furthermore, most of megafauna have been removed with very little documentation or historical understanding of what the community was like. Thus, our ability to separate anthropogenic impacts from the natural dynamics of the system is severely compromised. Yet, anthropogenic alteration of most environmental systems occurs via an accumulation of impacts, large and small.

28 North Atlantic Swordfish Is there a Shifting Baseline here? The average North Atlantic swordfish caught in the 1960s weighed 300 pounds. By the late 1990s, the average was 100 pounds (NOAA - ICCAT).

29 Swordfish Life History Geographic range: Gulf Stream (western North Atlantic), extending north into the Grand Banks; eastern Atlantic along Africa /Europe Life span: 9+ years Maximum size: Up to 1,165 pounds Reproductive maturity: Between 4 to 5 years in females Reproduction: Females produce variable number of eggs: - from 1-16 million in a 370-pound female - to 29 million in a 600-pound female

30 History of Swordfish Fishery 1920s Recreational fishery begins, primarily from Massachusetts to New York 1960s Longline gear introduced in commercial fishery, replaces harpoons 1966 International Convention for Conservation of Atlantic Tunas signed creating International Commission for Conservation of Atlantic Tunas (ICCAT) 1970s Recreational fishery develops in Florida 1990 ICCAT passes first recommendation on swordfish, calling for harvest reductions of undersized North Atlantic swordfish; 1999 ICCAT establishes 10-year rebuilding program

31 Swordfishiness Is there a problem? Swordfish stocks in trouble worldwide - worst in N. Atlantic, questionable in Mediterranean and Pacific - starting in late 1990s. What actions were taken? U.S. NMFS set fishing limits, while conservation groups organized boycott of swordfish among chefs and restaurants starting in Did they succeed? ICCAT announced in 2002 that Atlantic swordfish stocks had made a "94% recovery". Boycotters claimed victory and said it showed their power, but fisheries managers disagree, saying it was response to recovery action implemented years before boycott.

32 Managing Sliding Fisheries Annual Swordfish Catch ( ) SCRS/2009/016 - SWO ATL Stock Assessment

33 Recent History of Swordfish Management 2000/2001 NOAA Fisheries implements several large time and area closures for pelagic longline fishing to reduce bycatch of juvenile swordfish and billfish 2002 Stock assessment determines stock biomass is 94 % of levels needed for maximum sustainable yield (B MSY ) 2004 NOAA Fisheries Service implements bycatch reduction measures in commercial fishery (Goal: reduce take of small-size fish) 2006 Stock assessment estimates that biomass approximately 99 % of B MSY 2007 U.S. regulations establish baseline quotas and develop methods for catch reporting of recreational fishers (Goal: do not overshoot the quota) 2009 North Atlantic swordfish is considered fully rebuilt

34 Managing Sliding Fisheries Empirical Observations Modelling Efforts Catch Data (logbooks / observers) ((NOAA Fisheries) Fishery Surveys Stock-Recruitment Data

35 F: Fishing Mortality (0 to 1) Monitoring the Swordfish Population B: Biomass (weight of fish) SCRS/2009/016 - SWO ATL Stock Assessment

36 Swordfish Fishery Benchmarks If we were looking at this issue from a conservation perspective, what metrics would we want to use to assess whether this stock has experienced a sliding baseline? Hint: How can we quantify ecological extinction

37 Change in size / Maturity ICCAT's minimum size limit 41 lbs. The average North Atlantic swordfish caught in the 1960s weighed 300 pounds. By the late 1990s, the average was 100 pounds (NOAA - ICCAT).

38 Change in size / Maturity SCRS/2009/016 - SWO ATL Stock Assessment

39 Changes in Distribution of Catches 1950s 1960s 1990s s 1980s

40 Extirpation: Stocks & Strategies Longline Large swordfish basking at the surface taken by harpoons in the Gulf of Maine and Mediterranean Other

41 Uncertainty, Temporal Resource Exploitation, Consistency and Conservation: Lessons from History (Ludwig et al. 1993) Although there is considerable variation in detail, there is remarkable consistency in the history of resource exploitation. We suggest that such consistency is in part due to the following: Large levels of natural variability mask effects of overexploitation Thus, initial overexploitation is not detectable until it is severe May 5, 2009 ( Problem with SBE CTD pressure sensors on Argo floats, recommendation to stop float deployments and return for repair Furthermore sliding baselines influence our attitutes towards nature In early March 2009 an expanded analysis of Argo surface pressures, revealed an increase in the occurrence rate of floats exhibiting negative surface pressures from floats deployed in 2007 and later.

42 Uncertainty, Resource Exploitation, and Conservation: Lessons from History (Ludwig et al. 1993) Five Principles of Effective Management : Our lack of understanding and inability to predict require a cautious approach to resource exploitation. Here are some suggestions for management: 1) Study human motivation and responses as part of the system 2) Act before scientific consensus is achieved 3) Rely on scientists to recognize problems, but not to remedy them (interdisciplinary problems / external pressures) 4) Distrust claims of sustainability. Be always ready to act 5) Confront uncertainty. Effective policies are possible under conditions of uncertainty, but they must take uncertainty into account

43 Those who cannot remember the past are condemned to repeat it - J. Santayana

44 The future's uncertain and the end is always near - J. Morrison (Roadhouse Blues)

45 We are not in Kansas any more - Wizad of Oz

46 Sliding Baselines - References Pauly, D (1995) Anecdotes and the shifting baseline syndrome of fisheries. Trends in Ecology and Evolution, 10(10):430. Pauly, D (2001) Importance of historical dimension policy management in natural resource systems. ACP-EU Fisheries Research Report 8 Dayton PK, Tegner MJ, Edwards PB and Riser KL (1998) Sliding baselines, ghosts, and reduced expectations in kelp forest communities. Ecological Applications, 8(2): Papworth SK, Rist J, Coad L and Milner-Gulland EJ (2009) Evidence for shifting baseline syndrome in conservation. Conservation Letters, 2(2):

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